Predicting Future Climate Change

Sylvia Knight, Atmospheric, Oceanic and Planetary Physics,

University of Oxford

The Day After Tomorrow

The science of climate change

• What is “climate” and why do we think it is changing?

• How can we predict climate when we can’t predict the weather?

• What are the main uncertainties in climate prediction?

• Simulating climate change: the science of climate modelling.

• Using spare capacity on personal computers for global climate prediction.

“Climate is what we expect; weather is what we get”

Climate is the statistics of the weather• Mean annual Indian Rainfall• Average October temperature in Astana• How often hurricanes happen in the Gulf of

Mexico

What is the Climate?

”Climate is what we expect, weather is what we get”

“In the light of new evidence and taking into account the remaining uncertainties,most of the observed warming over the last 50 years is likely to have been due to the increase in greenhouse gas concentrations”

Source: Intergovernmental Panel on Climate Change (IPCC) Third Assessment Report, 2001

Mountain glaciers of the Zailiiskiy Alatau

Source: Stephan Harrison, University of Oxford

• 416 glaciers

• Losing 0.7% of their mass per year (1955 – 2000)

• Glaciers are mainly small, with rapid response times

• 75-80% of water supply derived from glaciers and permafrost

Multiyear fluctuations of mean January monthly temperatures in the northern Zailiiskiy Alatau range (1– Almaty, 847 m asl, 2 –Bolshaya Almatinskoye Lake, 2516 m asl). Solid line is the 10-year moving average.

-18

-16

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01870 1890 1910 1930 1950 1970 1990

YearsT,C

1

2

Source: Stephan Harrison, University of Oxford

Tuyuksu Glacier

• 5km long• 4km2 in area• Measurements since 1870• Retreated throughout 20th century• Retreated 10m in 2000

Tuyuksu Glacier mass balance

Source: Stephan Harrison, University of Oxford

Climate is determined by factors like:

•Solar irradiance (power output of the sun)•Volcanic activity•Atmospheric composition (greenhouse gases etc...)•Positions of continents, ice-sheets etc.

We call these the ‘forcing mechanisms’

SUN

Sunlightpasses

through the atmosphere..

..and warms the earth.

..most escapes to outer spaceand cools the earth...

Infra-red radiationis given off by the earth...

…but some IR is trapped by some gases in the air,

thus reducing the cooling….

Source: Ellie Highwood

Energy in the climate system

Leaky Bucket

Weather/ climate model

MODEL

observationsWhat we know willchange in the future

• Models are simplified versions of real systems

• In the case of climate prediction, what we mean by a model is a set of equations that represents how the atmosphere and oceans behave – how temperature patterns develop, how winds blow etc.

General Circulation Model of the Atmosphere:

3 Equations of Motion Equation of StateEnergy EquationMass Conservation

} 3D wind fieldTemperaturePressureDensity

• Convection scheme • Cloud scheme • Radiation scheme• Sulphur cycle• Precipitation• Land surface and vegetation• Gravity wave drag scheme

The Model also includes:

Each of these equations is evaluated at each point in the model [96 longitudes by 73 latitudes by 19 vertical levels] every half hour

timestep

Models forced by natural changes

Models forced by anthropogenic changes

Models forced by anthropogenic and natural changes

Source: IPCC Third Assessment Report

Atmospheric Carbon Dioxide Concentration

Source: IPCC Third Assessment Report, 2001

We can produce very detailed predictions of climate change with no idea of how reliable they

might be

2080 temperature change (K)

2080 precipitation change (%)

Source: Dr. Mat Collins, Hadley Centre

Do you trust a weather forecast?

Double Pendulum

Courtesy of Ross Bannister

Initial speed400.1 degrees/ sec

Initial speed400.0 degrees/ sec

Does the Flap of a Butterfly's Wing in Brazil Set Off a Tornado in Texas?Ed Lorenz

CHAOS

The climate is like a game of roulette…

Parameters perturbed• Critical Relative Humidity (RHcrit)

- related to the cloud cover distribution in a grid box.• Accretion constant (CT)

- related to growth of rain droplets and lifetime of clouds.• Condensation nuclei concentration (CW)

- affects water holding capacity and lifetime of clouds.• Ice fall velocity (VF1)

10.5 – 2.0VF15x10-52x10-5 – 5x10-4CW - sea2x10-41x10-4 – 2x10-3CW - land1x10-45x10-5 - 4x10-4CT0.70.5 – 0.95 (0.6 – 0.9)RHcrit“Standard” valuesRange:Parameter:

Climate Sensitivity

So for a complete climate forecast, we need to find out what hundreds of thousands of models do….

Initial conditions: all the possible ‘butterflies’

Forcing mechanisms: carbon dioxide, volcanoes …

‘Parameters’ – climate models aren’t perfect

Hundreds of Thousands of possible model variants…

Standard model set-up

Perturbedphysics

ensemble

Initialconditionensemble

Boundary Conditions (forcing) ensemble

Overall em

bedded-ensemble

www.climateprediction.net

Experiment 1 (September 2003 – end 2005)

How does each model react when carbon dioxide is doubled?

→ Investigate the sensitivity of the models to changes in the composition of the atmosphere

Experiment 2 (February 2006)

How well does each model do at reproducing the climate of 1950-2000?

→ Find out which models we believe more than others

What climate does each model predict for 2000 - 2050?

→ A probability-based climate forecast for the 21st century

Climateprediction.net experiment design

Climate Sensitivity: the equilibrium response of globally averaged temperature to a doubling of Carbon Dioxide

47334 climateprediction.net simulations passing initial quality control

Courtesy of Ben Sanderson

Traditional range

High risk of substantial warming even with today’s greenhouse gas levels

Can we really talk about a ‘safe’ stabilisation limit?

Standard model version

Low sensitivity model

High sensitivity model

Regional responses: temperature and precipitation

Regional Behaviour – European PrecipitationMediterranean Basin Northern Europe

WinterWinter

SummerSummer

Annual Annual

Unpublished analysis from climateprediction.net: Source: David Stainforth

Record hot events are more likely in a generally warmer world

Summer 2003 temperatures relative to 2000-2004

From NASA’s MODIS - Moderate Resolution Imaging Spectrometer, courtesy of RetoStöckli, ETHZ

Excess mortality rates in early August 2003 indicate 22,000 - 35,000 heat-related deaths

Daily mortality in Baden-Württemberg

Was the hot summer of 2003 due to climate change?

Anthropogenic emissions of greenhouse gases have doubled the risk of a summer like 2003

By 2050, it could be that hot every other summer

We can’t say.

In law, if you can show that the actions of a person or organisation have doubled the risk of a damaging event, you can claim compensation for the damage caused

Fossil fuels are artificially cheap, since we pay for the cost of extraction, and not for the cost of the impacts

If politicians were to apply the “polluter pays principal” to the producers of fossil fuels, it may well make more sense to sell carbon neutral fuel (from a renewable energy source, or where an equal amount of carbon has been removed from the system in compensation)

What is Carbon dioxide Capture and Storage (CCS)?

Source: Claire Gough, Tyndall Centre for Climate Change Research

• More acceptable solution than nuclear power?

• Current price of carbon is £15 per tonne CO2

• Research shows cost of capture, transport and storage from UK power stations to be between £25 and £60 per tonne CO2

The technology is already in use• Sleipner: 1 MTCO2 per annum since 1996 stored

in saline aquifers below North Sea.

• Weyburn Enhanced Oil Recovery Programme: 20 Mt CO2 will be stored. CO2 supplied via a 205 mile pipeline from plant in North Dakota.

• In Salah, Algeria: Storage in Hydrocarbon Reservoirs CO2 to be removed from the gas produced and reinjected into depleted gas reservoirs

“We have no objection in principle to the capture of carbon dioxide and its storage in underground formations but the pursuit of this technology is a distraction from the real priorities of implementing renewable energy and energy efficiency technologies which are available right now. We've given tax breaks to companies for getting oil and gas out of the ground, we shouldn't subsidise them to put the subsequent pollution back underground."

Bill Hare, Greenpeace. Guardian 15/06/05

2005 U.K. Budget:"Carbon capture and storage […] is likely to

prove a critical technology in global carbon reduction strategies. The Government is therefore examining how it might support the development of CCS in the Climate Change Programme Review, including the potential for new economic incentives."

www.climateprediction.net

Standard Visualisation Package

Since September 2003, 105,000 participants in 142 countries (8 in Kazakhstan)have completed 115,000 45 -year model runscomputed 8 million model years donated 8,000 years of computing time

Temperature 2000 - 2100

Will the results of experiment 3 look like this made up figure?